The present invention relates to a quick connect fluid coupling with an improved retainer that secures the tube bead over its entire circumference.
Quick connect couplings are used to quickly and securely connect a tube within a housing bore or to a second tube. Quick connect couplings are utilized in most modern vehicles to connect brake lines, air conditioning lines, power steering lines and other high-pressure and vacuum lines.
In standard quick connect couplings a retainer is received within a female housing bore. The retainer has a plurality of arms which extend radially inwardly in a direction moving axially into the bore. The tube has a radially greater diameter bead which moves into the bore and flexes the arms outwardly. The axially and radially innermost ends of the arms define an inner diameter approximately equal to the other diameter of the tube at locations other than the bead. As the tube is inserted further into the bore, the bead forces the arms radially outwardly, and moves axially past the arms. Once the bead has moved axially beyond the arms, the arms spring back to a position where they are radially outwardly of the tube, and axially between the tube bead and outer end of the bore. The tube is then fully inserted, and the retainer securely retains the tube within the housing.
While quick connect couplings having flexible arms that latch behind the bead are widely used, they do have some deficiencies. The retention is limited to the specific contact points at the circumferentially spaced ends of the arms. Also, these retainers vary from design to design and their operation is highly dependent on the material, length, angle, thickness, and the number of arms. Temperature extremes diminish the effectiveness of the arms. The spaced arms become brittle when cold and softened when hot. Also, the flexible arms trap the tube in the connector, but do not offer significant side load support to the coupling. Further the flexible arms require a relatively large insertion distance because the tube bead must be inserted past the flexible arms.
The height of the tube bead must be relatively large to provide enough surface on the side of the bead for the flexible arms to latch. The height remains relatively constant across various tube diameters. Therefore, the smaller the tube diameter, the larger the percentage of deformation radially outwardly of the tube material. The material of the tubes typically fails if deformed more than 50%. For tubes of relatively small diameter, such as less than xc2xdxe2x80x3, the tube bead has typically been deformed up to 35% to 40%. At larger tube diameters, such as greater that xc2xdxe2x80x3, the tube bead is deformed over 15%. In one known type tube having a diameter of {fraction (5/16)}xe2x80x3 or xe2x85x9cxe2x80x3, the beads are typically deformed 32%.
In one know type of tube, a {fraction (5/16)}xe2x80x3 tube diameter had a 0.05xe2x80x3 height tube bead, or 32% deformation. In that same type of tube, a xe2x85x9cxe2x80x3 tube diameter required a 0.06xe2x80x3 tube bead height, or 32% deformation. In one other standard prior art quick connect tube, a {fraction (5/16)}xe2x80x3 tube required 0.062xe2x80x3 tube bead height, or 39% deformation. A xe2x85x9cxe2x80x3 tube diameter had a 0.065xe2x80x3 tube bead height, or 35% deformation. A xc2xexe2x80x3 tube diameter required 0.070xe2x80x3 tube bead height, or 19% deformation. A 1xe2x80x3 tube diameter required a 0.080xe2x80x3 tube bead height, or 16% deformation.
The excessive deformation thus weakens the tube near the tube bead, and provides a source of potential failure. The large beads are needed since the retainer only contacts the tube at circumferentially spaced points.
It has been proposed to utilize a collet retainer disposed within an axial bore of the connector housing. The proposed collet generally comprises a ring having a split to provide radial expendability. Upon insertion of the tube into the housing, the collet is expanded radially by the tube bead. After the tube bead is inserted past the collet, the collet contracts onto the tube behind the tube bead. Often the collet does not contact the entire circumference of the bead.
In one quick connect coupling, when the coupling is pressurized, the collet slides under a ledge in the housing which prevents the collet from expanding radially. However when the quick connect coupling is not pressurized, the collet may inadvertently expand radially and release the tube. Thus, the proposed collets have not been successfully utilized.
The present invention provides a quick connect coupling which ensures the proper positioning of a radially expandable collet retainer to prevent the inadvertent release of the tube. A practical collet retainer provides a secure connection around the majority of the tube bead circumference. Thus, a smaller tube bead may be used that does not result in material fatigue. The quick connect coupling generally includes a housing having an axial bore extending into the housing and expanding from an entrance. A tube having a tube bead of increased diameter is insertable into the axial bore of the housing. The tube is retained within the housing by a radially expandable collet disposed within the housing bore. The collet acts as a wedge between the tube bead and the housing over the entire circumference of the tube bead. In one embodiment, a spring within the housing biases the collet toward the entrance of the housing, thereby keeping the collet in proper position. In another embodiment, no spring is used.
The inventive collet retainer is relatively insensitive to variation compared to known quick connect retainers using flexible arms. Since the collet retainer provides a wedge between the tube bead and the housing around the entire circumference of the bead, there is more margin for manufacturing tolerances. Preferably, the collet is normally contracted and is sufficiently biased toward a contracted state to retain the collet between the tube bead and the housing. In one embodiment which can be used in extreme conditions, the spring biases the collet against a portion of the housing, thereby ensuring the proper positioning of the collet within the housing and preventing the inadvertent radial expansion of the collet. The inventive quick connect coupling provides stronger side load support to the connection while also permitting a shorter insertion distance of the tube into the housing because the collet provides support to the connection around the entire diameter of the tube. With the inventive collet, the diameter of the tube bead need be increased less than 20% for tube diameters under xc2xdxe2x80x3, and preferably only 5% to 15% for tube diameters xc2xdxe2x80x3 or greater.